Negative electrode active material for secondary battery and method of manufacturing the same

Abstract

Provided is a negative electrode active material for a secondary battery including a core-shell composite including: a core including a silicon oxide (SiO x , 0<x≤2) and a metal silicate in at least a part of the silicon oxide; and a shell including a metal-substituted organic compound, wherein the metal of the metal silicate and the substituted metal of the organic compound are independent of each other, wherein each of the metal of the metal silicate and the substituted metal of the organic compound includes an alkali metal or an alkaline earth metal.

What is claimed is: 
     
         1 . A negative electrode active material for a secondary battery comprising a core-shell composite including:
 a core including a silicon oxide (SiO x , 0<x≤2) and a metal silicate in at least a part of the silicon oxide; and   a shell outside the core and including a metal-substituted organic compound,   wherein the metal of the metal silicate and the substituted metal of the organic compound are independent of each other, wherein each of the metal of the metal silicate and the substituted metal of the organic compound includes an alkali metal or an alkaline earth metal,   wherein a value of the following Equation (1) is 0.02 to 0.18 in XPS analysis of a surface of the core-shell composite:
   [ M]/[C]   (1)
 
   wherein M is a substituted metal of the organic compound, [M] is an M content (at %) measured by XPS analysis, and [C] is a C content (at %) measured by XPS analysis.   
     
     
         2 . The negative electrode active material for a secondary battery of  claim 1 , wherein the metal of the metal silicate and the substituted metal of the organic compound are the same. 
     
     
         3 . The negative electrode active material for a secondary battery of  claim 1 , wherein a concentration of the substituted metal on an outer surface of the core-shell composite is lower than a concentration of the substituted metal in an interface between the core and the shell, based on a cross-section through a center of the core-shell composite. 
     
     
         4 . The negative electrode active material for a secondary battery of  claim 1 , wherein the metal silicate is one or more selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, and magnesium silicate. 
     
     
         5 . The negative electrode active material for a secondary battery of  claim 1 , wherein the core includes 10 to 95 parts by weight of the metal silicate with respect to 100 parts by weight of the silicon oxide. 
     
     
         6 . The negative electrode active material for a secondary battery of  claim 1 , wherein the organic compound is an aqueous organic compound including one or more functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an amine group, and an amide group. 
     
     
         7 . The negative electrode active material for a secondary battery of  claim 6 , wherein the organic compound includes a catechol-based compound. 
     
     
         8 . The negative electrode active material for a secondary battery of  claim 6 , wherein the organic compound is one or more aqueous polymers selected from the group consisting of polyacrylic acid (PAA), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), regenerated cellulose, starch, alginic acid, guar gum, gum arabic, and polyvinyl pyrrolidone (PVP). 
     
     
         9 . The negative electrode active material for a secondary battery of  claim 1 , wherein the shell has an average thickness of 0.1 to 100 nm. 
     
     
         10 . The negative electrode active material for a secondary battery of  claim 1 , wherein in the core-shell composite, a weight ratio of the shell to the core is 0.1 to 10. 
     
     
         11 . The negative electrode active material for a secondary battery of  claim 1 , wherein the core-shell composite further includes amorphous carbon. 
     
     
         12 . A method of manufacturing a negative electrode active material for a secondary battery, the method comprising:
 a) a pretreatment process of mixing a silicon compound and an alkali metal or alkaline earth metal precursor and performing a heat treatment to dope a metal into the silicon compound; and   b) a composite production process of mixing the metal-doped silicon compound with an organic compound and performing a heat treatment to prepare a composite,
 wherein a value of the following Equation (1) is 0.02 to 0.18 in XPS analysis of a surface of a core-shell composite:
   [ M]/[C]   (1)
 
 
    wherein M is a substituted metal of the organic compound, [M] is an M content (at %) measured by XPS analysis, and [C] is a C content (at %) measured by XPS analysis.   
     
     
         13 . The method of manufacturing a negative electrode active material for a secondary battery of  claim 12 , wherein the alkali metal or alkaline earth metal precursor of the pretreatment process of a) includes:
 a hydride, a hydroxide, an oxide, or a carbonate of metals including one or more selected from the group consisting of Li, Na, Mg, and K; or   metal particles including one or more selected from the group consisting of Li, Na, Mg, and K.   
     
     
         14 . The method of manufacturing a negative electrode active material for a secondary battery of  claim 12 , wherein the pretreatment process of a) includes a heat treatment at 500 to 1000° C. under an inert atmosphere. 
     
     
         15 . The method of manufacturing a negative electrode active material for a secondary battery of  claim 12 , wherein in the composite production process of b), the organic compound is included at 5 to 50 wt % based on a total weight of the silicon compound and the organic compound. 
     
     
         16 . The method of manufacturing a negative electrode active material for a secondary battery of  claim 12 , wherein the composite production process of b) includes a heat treatment at 80 to 120° C. under an inert atmosphere. 
     
     
         17 . A secondary battery comprising a negative electrode including the negative electrode active material of  claim 1 .